I like the top-5 picks thing, but having everybody do it for the first round at the same time doesn't seem to be optimal. How about asking for the next 8 drafters to send you a top-5 list during the first round. After the first 8 are picked do another 8 with 4-hour windows to send in the top-5 list.
I'm drafting at 17, so what's the point of me sending a top-5 of: C. Long, J. Long, G. Dorsey, M. Ryan, V. Gholston - I would take any of those guys at 17, but they won't be there. I think it makes more sense to request my list after 8 or 12 people have already selected.
After the first round, I think it would be OK to get a top-5 from everybody in the entire next round each time (with a 12-hour or 24-hour return-the-list window) - since there will be a lot more variation in the lists there won't be many delays due to lists being completely picked already.